In today's energy conservation conscious world, finding ways to better insulate our homes, is foremost on the minds of a great many people. Many different materials have been used for such insulation. For example, fiberglass insulation provides good insulation characteristics for insulation of walls, ceilings, etc. of homes. However, a large number of homes have been built in the past without sufficient insulation in their walls. Obviously, it would be very costly remove and replace the walls of a home to retrofit them with insulation materials such as fiberglass. Accordingly, methods which would avoid such destruction of the walls are extremely advantageous.
One of the road blocks to achieving maximum energy efficiency in residential home weatherization retrofits is the type of construction encountered in homes built prior to and during the 1970's. “Balloon” construction was common in residential construction and the exterior walls of the house are not filled with insulation, they are hollow. In some instances, the wall cavities were open to the attic on the top, and the basement below. Since attics and basements are full of damp cold air, convective air current laden with this cold, moist air circulated within the walls.
The United States has placed an increased emphasis on the energy efficiency of residential and commercial buildings and provided stimulus money for these weatherization programs. It is believed that approximately 40% of a building's energy costs are related to heating and cooling losses attributable to air movement in and out of the structure. Therefore, stopping air movement in this manner has one of the largest impact on reducing energy costs relating to heating and cooling, offering even more value than replacing windows and installing new HVAC equipment. Foam insulation and sealants, combined with other structural materials such as oriented strand board (“OSB”) and drywall, all combine to create the building's air barrier. A continuous air barrier is required for maximum energy conservation.
Various foam materials have been used in the past in an attempt to retrofit wall cavities with insulation materials. For example, ureaformaldehyde and phenolformaldehyde foams have been previously used by pumping such foam into the wall cavity through a hole placed in the walls. Ureaformaldehyde foam has a number of disadvantages including friability, release of toxic formaldehyde if poorly applied, shrinkage with subsequent loss of insulation effectiveness, and limited warm temperature resistance that prohibits its use in walls in warmer climates and in attics. The major drawback of loose-fill insulation products is settling with time, creating uninsulated voids in wall cavities. Impracticality prohibits the use of more conventional insulation materials (such as, urethane board stock, fiberglass, polystyene, foamed glass, polyolefin foams) to retrofit wall sections simply because of the difficulty of manufacturing and/or installing at the site without extensive building damage.
Polyurethane and polyisocyanurate foams are well-known as effective insulation materials. However, using such prior polyurethane or polyisocyanurate foams to retrofit wall cavities with insulation has met with certain difficulties. First, the polyurethane or polyisocyanurate insulating foams have been too dense to make them economical as insulation for wall cavities. For example, most walls contain cavities in the range of three and five-eighths inches (equivalently 9.21 cm) thick. The amount of polyurethane or polyisocyanurate foam needed to fill these large cavities cannot be economically justified in terms of the insulation obtained by the foam, e.g., satisfactory insulation characteristics would be economically obtained with a foam about 2 inches (equivalently 5.1 cm) thick. Moreover, the prior polyurethane or polyisocyanurate foams used to retrofit wall cavities with insulation have had other problems because they have rise times which greatly exceed their gel or set times. Thus, such a foam first sets within the wall cavity to such an extent that the pressure generated within the cavity causes damage as the foam completes its expansion. Also, excess foam inadvertently admitted into the wall cavity will not continue to extrude through the access hole in the wall, but rather will continue to expand creating internal pressure pushing on the walls of the cavity and in many instances causing buckling or even cracking of the walls.
At least one entity is believed to offer a slow-reacting, low density, open-celled polyurethane foam which is dispensed using high pressure impingement-mixing equipment. As with any high pressure dispensing equipment, the foam is initially dispensed as a liquid, turning to a froth after a period of time. While a liquid, it seeps out through penetrations in the floor boards at the bottom of the wall cavity, damaging flooring surfaces. Once it begins to expand (at approximately at least 20 seconds after application), the expansion is believed to be vigorous, leading to drywall damages. The foam is blown with water through the reaction of water and MDI forming carbon dioxide. This foam is believed to be applied carefully, using many holes in the wall cavity, and requiring that the baseboard area be taped off to prevent seepage of the dispensed foam.
It is also believed that acrylic-based latex type foams have been tried with limited success in that the acrylic-based latex type form has little or no apparent structural integrity, as it is not crosslinked, leading to slumping and degradation within the wall cavities in a relatively short amount of time after installation.
Therefore, it is easily seen that what is needed is a way to dispense foam into cavities in which there is minimal to no damage to existing drywall and further which flows around obstructions (e.g., electrical boxes) within the wall cavity, employs a foam with structural integrity, preferably crosslinked, thereby forming a continuous air barrier in the exterior walls of the structure.